1. Field of the Invention
The present invention generally relates to a flexible cover for protecting an object subjected to an airstream in open-air transport and, more particularly, to a cover for personal watercraft, watercraft, snowmobiles and the like, that conforms closely to the object it protects by differential pressure.
2. Background Art
Flexible covers are widely used in open-air transport to protect objects exposed to an airstream when being towed by a vehicle. For instance, personal watercraft, watercraft and snowmobiles are partially covered during transport to be protected from the elements of weather and from windblown debris inherent to open-air transport.
At highway speeds, looser portions of the protective cover have been known to whip and buffet. In addition to causing some noise, the whipping and buffeting may result in the cover being blown off by the airflow, or the cover being ripped open, thereby temporarily exposing the object being transported.
U.S. Pat. No. 5,997,071, issued on Dec. 7, 1999 to Mazzarelli, discloses a protective cover secured to the object it protects by differential pressure, to overcome the above-cited problems. More precisely, the cover protects a substantial portion of an object, and exhaust apertures are defined in the cover. The exhaust apertures are each covered by a tear-shaped vent member having an open end. The open end of each vent member faces away from a direction of tow. The airstream that results from the tow circumvents the vent members, and the latter are shaped and positioned such that a pressure drop is created at the open end of the vent members. Therefore, as the vent members are each positioned over one exhaust aperture, air concealed between the cover and the object being transported moves out from under the cover through the exhaust apertures. This outflow of air will cause the flexible cover to mold or conform closely to the object that it protects.
U.S. Patent Application Publication No. US 2002/0069947, published on Jun. 13, 2002, from Frechette et al., also describes a flexible protective cover secured to the object it protects by differential pressure. This publication discloses an alternative approach to creating the differential pressure between an interior of the cover and an exterior thereof. In this publication, exhaust apertures are provided in surfaces of the flexible protective cover that face away from the direction of transport. More specifically, two surfaces are identified as being disposed vertically in reference to the direction of travel, and as being disposed on the leeward side of the object. These surfaces are exposed to lower pressures and are hence provided with apertures through which air exhausts from the interior of the cover.
A drawback of the prior art pressure differential systems is that they involve costly solutions. For instance, vent members must be formed of a material having sufficient structural integrity to withstand an airstream. Such vent members must therefore be manufactured according to more complex processes than that typically involved in fabricating covers, such as molding.
Also, some types of pressure differential systems are not efficient on all types of covers. For instance, the pressure differential system of U.S. Patent Application Publication No. US 2002/0069947 requires a given geometry of the objects being covered, for natural low pressure zones providing sufficient suction to be formed. The geometry of some objects does not allow for suction of sufficient magnitude to be created.